Kitchen appliance

ABSTRACT

An electric kitchen appliance has a pot for receiving food to be processed using the electric kitchen appliance. An ultrasound transmitter and an ultrasound receiver are provided in order to determine the fill level of the food in the pot. The ultrasound transmitter and the ultrasound receiver are attached to the upper edge of the pot such that an ultrasound signal can be transmitted onto the surface of the food by the ultrasound transmitter, and an ultrasound signal reflected by the surface of the food can be received by the ultrasound receiver. In this manner, an electric kitchen appliance is provided which allows the fill state of the food in the pot to be determined in a simple and reliable manner.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the National Stage of PCT/EP2016/051976 filed onJan. 29, 2016, which claims priority under 35 U.S.C. § 119 of GermanApplication No. 10 2015 101 299.5 filed on Jan. 29, 2015, thedisclosures of which are incorporated by reference. The internationalapplication under PCT article 21(2) was not published in English.

The invention relates, in the first instance, to a kitchen appliancedesigned with an electrical power supply, which has a pot for purposesof accommodating foodstuffs to be processed with the kitchen appliance,and forming a foodstuffs fill surface, whereby for purposes ofdetermining the fill state of the foodstuffs in the pot an ultrasoundtransmitter and an ultrasound receiver are provided, and the pot has apot wall with a wall thickness and a cylindrical or conically developedinternal surface.

The invention further concerns a kitchen appliance provided with anelectrical power supply with a pot for purposes of accommodatingfoodstuffs to be processed with the kitchen appliance.

Kitchen appliances that have a pot for purposes of accommodatingfoodstuffs to be processed with the electrical kitchen appliance, andalso frequently a lid for purposes of covering the pot, are well knownin the prior art. For example, reference should be made to pressurecookers, and also to multifunctional kitchen machines. The latter are asa general rule provided with such a pot, which enables the accommodationof foodstuffs such that these can be processed in various ways. Suchprocessing of the foodstuffs can, for example, take the form ofcomminution, stirring or kneading. Moreover, there are such pots ofkitchen machines of known art that provide additional functions, such asweighing, and/or heating of the foodstuffs contained therein.

When filling the foodstuffs into such a pot, it is often of greatimportance to avoid overfilling the pot. For example, if the pot isfilled with foodstuffs such as a liquid beyond a predetermined amount,the risk can exist that during the processing of the foodstuffs, e.g.during a mixing process, the foodstuffs exit from the pot. This can beprevented by providing the electrical kitchen appliance with a filllevel determination device for purposes of determining the fill level ofthe foodstuffs in the pot. Here the fill level determination device doesnot have to enable a regular quantitative measurement of the fill levelof the foodstuffs in the pot. On the contrary, it is generallysufficient for the fill level determination device to detect whether thefill height of the foodstuffs in the pot is in fact below a maximumpermissible fill height.

From EP 2 633 790 B1 an electrical kitchen appliance with a fill leveldetermination device is already of known art. It is described thereinthat a transmitter and a receiver for purposes of transmitting orreceiving radiation are mounted on the lid in such a way that the filllevel in the pot can be detected even when the lid is open.

From US 2010/0058856 A1 a cup-form measuring device is of known art, inwhich the measuring device has an ultrasound sensor, which is arrangedon the upper edge of the cup, protruding into the interior of the cup.From GB 2 076 536 A a device for detecting a fluid level is of knownart, in which ultrasound transmitters and receivers are arranged at therear of a vessel wall, whereby the sound propagation within the wall ofthe vessel is essential for the determination of the fluid level. US2010/0000315 A1 shows an electro-optical device integrated into a lidfor purposes of detecting a liquid level in a container. JP 11113738 Adescribes a measuring device on the basis of an ultrasound sensor, whichis integrated into a handle of a vessel for purposes of detecting awater level when cooking rice. For purposes of detecting a liquid in avessel, FR 2 617 965 A1 describes a sensor for purposes of exciting anddetecting elastic waves, which passes through an opening in the wall ofthe vessel.

From US 2004/0112225 A1 a cooking vessel with two temperature sensors isof known art. The evaluation of the temperature sensors is used todeactivate the heating if a difference between the temperatures measuredby the two sensors is greater than, or equal to, a predeterminedtemperature difference.

Starting from the prior art as described above, the invention isconcerned with the task of determining, simply and reliably, the filllevel in a pot of a kitchen appliance provided with an electrical powersupply.

This task is solved in the first instance by a kitchen appliance whereinthe aim is that the ultrasound transmitter and/or the ultrasoundreceiver is arranged for purposes of transmitting or receivingultrasound in the region of the cylindrical or conically developedinternal surface, with the ultrasound transmitter and/or the ultrasoundreceiver forming a part of the cylindrical or conically developedinternal surface, or an arrangement of the ultrasound transmitter and/orthe ultrasound receiver within the wall thickness of the pot wall havingthe cylindrical or conically developed internal surface, for purposes ofapplying ultrasound from above onto the foodstuffs fill surface and forpurposes of receiving ultrasound reflected upwards from the foodstuffsfill surface.

The task is further achieved by a kitchen appliance wherein the aim isthat a heating element is arranged on the wall of the pot, a heatingmonitoring device is provided, with which the heating behaviour of theheating element can be monitored and from which a heating signaldependent on the heating behaviour of the heating element can beoutputted together with a fill level checking device, to which theheating signal can be supplied, and from which a fill level check offoodstuffs introduced into the pot can be carried out with regard to afill level above or below a maximum permissible fill height.

The ultrasound transmitter and the ultrasound receiver are mounted onthe pot and thus not, for example, on a lid provided for the pot. Inparticular, when a lid is provided that is detachable from the pot, thishas the advantage that the determination of the fill level of thefoodstuffs in the pot can take place independently of the position ofthe lid, and in particular also irrespectively of whether the lid isattached at all to the electrical kitchen appliance. The provision ofthe ultrasound transmitter and the ultrasound receiver on the upper edgeof the pot also has the advantage that an ultrasound signal can alwaysbe transmitted from the top to the bottom of the foodstuffs, even whenthe fill levels of the foodstuffs in the pot are very high.

In principle, the ultrasound transmitter and the ultrasound receiver canbe positioned on the wall of the pot in a continuation of the wall, e.g.they can also be positioned such that they can be detached. Inaccordance with a preferred development of the invention, however,provision is made for the ultrasound transmitter and the ultrasoundreceiver to be integrated into the wall of the pot. This ensures thatthe ultrasound transmitter and the ultrasound receiver are captivecomponents of the pot, and also has hygienic advantages, since when theultrasound transmitter and the ultrasound receiver are integrated intothe wall of the pot, the latter can be manufactured with a smoothsurface, which makes it easier to clean.

Furthermore, it is in principle sufficient if one ultrasound transmitterand one ultrasound receiver are provided. In accordance with a preferreddevelopment of the invention, however, the ultrasound transmitter andthe ultrasound receiver are part of a sensor ring designed on the upperedge of the pot, which has a multiplicity of sensors and thus at leastone further sensor. In principle the further sensor can also be anultrasound sensor. However, provision is preferably made for the furthersensor to be a sensor that differs from an ultrasound sensor, e.g. it isa temperature sensor or an “artificial nose”. By an “artificial nose” ismeant an “electronic nose”, which in the narrow sense means chemosensorymeasuring systems that are based on the biological odour.

Hereby it is not possible to determine primary odour properties, insteadcompositions of gas mixtures are analysed and then reinterpreted asodours. For further details, reference is made, for example, to theessay “Chemosensorics and Odour Measurement”, Peter Boeker, Institutefor Agricultural Engineering, University of Bonn, in AgrartechnischeForschung 7 (2001), No. 4, Pages 77-81.

In accordance with the invention it is essential that the ultrasoundtransmitter and the ultrasound receiver can be used to determine thefill level of the foodstuffs in the pot by way of an ultrasound signaltransmitted to the surface of the foodstuffs and reflected from thesurface of the foodstuffs. In accordance with a preferred development ofthe invention, however, the ultrasound transmitter has an additionalfunction. According to this preferred development of the invention, anultrasound controller is provided, by means of which the ultrasoundtransmitter can be activated such that the pot is cleaned at the sametime as the fill level is determined. This means that the ultrasoundcontroller activates the ultrasound transmitter for purposes of potcleaning with a type of ultrasound signal such that the wall of the pot,at least in some regions, excites oscillations of the type that enablethe release of any contamination that may be located there. Thispreferred configuration of the invention is particularly advantageousbecause cleaning by means of the ultrasound signal does not require anyadditional time, but rather can take place at the same time as thedetermination of level by means of the ultrasound signal transmittedonto the surface of the foodstuffs in the pot. With regard to differentsound intensities, which may be used, on the one hand, for determiningthe fill level, and on the other hand for cleaning purposes, provisioncan also be made for intermittent operation of the ultrasoundtransmitter in this respect. Provision can also be made for theultrasound sensor and the ultrasound receiver to operate on the one handin a mode for purposes of detecting the fill level, and, on the otherhand in the cleaning mode, in particular if a different sound intensityis associated with the latter. These operating modes can then either befreely selected by a user, or can be predetermined by a control programof the kitchen machine.

The ultrasound transmitter and the ultrasound receiver can be mountedseparately from one another as different devices on the upper edge ofthe pot. In accordance with a preferred development of the invention,however, the ultrasound transmitter and the ultrasound receiver arecollectively designed as one transducer. This simplifies the design ofthe electrical kitchen appliance and reduces the costs because only asingle ultrasound device is required for the level measurement.

It is an important aspect of one configuration of the invention that theheating behaviour of the heating element can be monitored such that aheating signal that is dependent on the heating behaviour of the heatingelement can be evaluated in the context of a determination of the filllevel. The principle underlying this aspect of the invention is thatwhen there is constant activation of the heating of the heating element,the latter depends on the extent to which heat can be delivered tofoodstuffs introduced into the pot. The higher the fill level of thefoodstuffs in the pot, the more the heat that can be delivered to thefoodstuffs, so that there is a correspondingly lower heating of theheating element itself. This heating behaviour, that is to say, thedegree of heating of the heating element, can be determined by theheating monitoring device, whereby the latter outputs a correspondingheating signal to the fill level checking device, which as a function ofthis heating signal can check whether the fill level of the foodstuffsin the pot lies above or below a maximum permissible fill height.

In principle any device with which the heating, that is to say, theheating behaviour of the heating element, can be detected, is suitableas a heating monitoring device. In accordance with a preferreddevelopment of the invention, however, a thermocouple and/or anelectrical ohmmeter is provided as the heating monitoring device. Withthe thermocouple, the temperature of the heating element can be detectedin a direct manner. An electrical ohmmeter can detect the temperature ofthe heating element by way of the principle that the electricalresistance of the heating element increases with increasing temperatureof the heating element. Assuming that an appropriate calibration isavailable, the temperature of the heating element can thus be detectedwith the thermocouple or with the electrical ohmmeter such that anadmissible, or too high a, filling of the pot with the foodstuffs can bedetected by means of the fill level checking device.

The heating element can be provided on the wall or on top of the wall ofthe pot. In accordance with a preferred development of the invention,however, the heating element is integrated into the wall of the pot. Inparticular this has also hygienic advantages, since in this way the wallof the pot can be designed to be smooth, which facilitates cleaning.

In what follows, various embodiments are described in more detail forpurposes of explaining the invention with reference to the figures. Inthe figures

FIG. 1 shows schematically an electrical kitchen appliance in accordancewith a first preferred example of embodiment of the invention, with anultrasound transmitter and an ultrasound receiver for purposes of leveldetermination, and

FIG. 2 shows schematically an electrical kitchen appliance in accordancewith a second preferred example of embodiment of the invention with astrip-form heating element for purposes of level determination.

FIG. 1 shows schematically an electrical kitchen appliance 1 with a pot2 for purposes of accommodating foodstuffs 3 to be processed with theelectrical kitchen appliance 1. A lid 4 serves to close the pot 2. Anultrasound transmitter 5 and an ultrasound receiver 6 are provided forpurposes of determining the fill level of the foodstuffs 3 present inthe pot 2, which in the present case is a liquid. For this purpose, theultrasound transmitter 5 and the ultrasound receiver 6 are mounted atthe upper edge of the pot 2, and specifically in the wall 12 of the pot2. In this way, a smooth surface is also provided in the interior of thepot 2, which is advantageous for hygienic reasons, and in particularpermits simple cleaning of the pot 2.

The pot can be a metal pot. The pot can consist of a steel material. Itcan, for example, be produced by the deep drawing process. The pot canalso consist of several materials, in particular a metallic part and aplastic part. The plastic part can be attached to the outside of themetal part. The plastic part can be provided over part of thecircumference of the pot, or can completely surround the pot. In thelatter case, however, the surround can only be designed over part of theheight of the pot. Also, for example, over an intermediate region of theheight, so that the foot region of the pot and the edge region do nothave any plastic surround (in the circumferential direction). Theplastic part can, for example, also be designed as a pot handle. Thearrangement of the ultrasound transmitter 5 and/or the ultrasoundreceiver 6 within the pot wall can also mean that these parts are atleast partly, but possibly also completely, accommodated in a plasticpart of the pot.

At the upper edge of the pot 2, preferably means that, with reference toa free internal height H of the pot, they are arranged within a regionb, which starts at the top edge 17, which is one third or less, forexample as little as 1/100, of the free internal height H. Thus allintermediate values, in particular in 1/100 steps, are also therefore ina region b, which ranges from 0.32 up to the top edge, or 1/100 or moredistant from the top edge. The boundary of this region—starting from thetop edge in the direction towards the bottom of the pot—can also bevaried in 1/100 steps. In particular, a region is also covered, which asregion b corresponds to a quarter of the internal height H, or aneighth, or a sixteenth of the internal height H.

In accordance with the preferred embodiment of the invention that can beseen in FIG. 1, the pot 2 of the electrical kitchen appliance 1 ismounted on a base 7 of the kitchen appliance In this base 7, in additionto a central control device 8 for the general control of the electricalkitchen appliance 1, are provided an ultrasound control unit 9 togetherwith an ultrasound evaluation unit 10. As indicated by the dashed linesI1, I2, the ultrasound controller 9 is connected to the ultrasoundtransmitter 5, and the ultrasound evaluation device 10 is connected tothe ultrasound receiver 6. The lines I1 and I2 can just be signalcables. In addition, another cable 18, 18′ can also be provided for thesupply of power to the ultrasound sensor and/or the ultrasound receiver.

The functioning of the electrical kitchen appliance 1 in accordance withthe preferred example of embodiment of the invention presently describedis now as follows:

The ultrasound transmitter 5 is activated with the ultrasound controller9 such that, as indicated by an arrow pointing obliquely downwards, anultrasound signal is transmitted downwards towards the surface 11 of thefoodstuffs 3 in the pot 2. There a partial reflection of the ultrasoundsignal takes place, such that a reflected proportion of the ultrasoundsignal runs back obliquely upwards and there impinges on the ultrasoundreceiver 6. The signal received by the ultrasound receiver 6 is thentransmitted to the ultrasound evaluation device 10, which in turn candetermine the level of the foodstuffs 3 in the pot 2 from the transittime of the ultrasound signal from the ultrasound transmitter 5 to theultrasound receiver 6. The electrical kitchen appliance 1 can only beswitched on when the fill level thereby determined is below apredetermined maximum fill level, and there is thus no overfilling ofthe pot 2. The corresponding functionality is implemented in the centralcontrol unit 8.

By virtue of the arrangement of ultrasound transmitter 5 and ultrasoundreceiver 6 at the upper edge of the pot 2, it is irrelevant whether thelid 4 is attached to the electrical kitchen appliance 1 or, how the lid4 is positioned on the pot 2. Since in accordance with the presentlydescribed preferred example of embodiment of the invention the lid 4 iscompletely removable from the pot 2, this is of great advantage, sincethe determination of the fill level of the foodstuffs 3 in the pot 2 iscompletely independent of the lid 4, and thus functions even when thelid 4 is not attached to the pot 2 at all.

In addition to the functionality of the ultrasound transmitter 5 forpurposes of transmitting an ultrasound signal to the surface 11 of thefoodstuffs 3 in the pot 2, by means of the ultrasound control unit 9, atype of activation of the ultrasound transmitter 5 is also possible suchthat the pot 2 is cleaned at the same time as the fill level isdetermined. For this purpose, an activation of the ultrasoundtransmitter 5 at a suitable frequency and a sufficiently large amplitudeis required in order to excite the wall 12 of the pot 2 into vibrationsthat are such as to enable a release of any contaminants that are fixedthere. A cleaning operation of this type thus takes no additional time,since it can take place at the same time as the detection of the filllevel of the foodstuffs 3 in the pot 2.

Conventionally, frequencies of 20 to 400 kHz are used, in particular forultrasound cleaning. Preference is given to frequencies in the rangefrom 20 to 15 kHz. However, higher frequencies are also beneficial forcleaning, in particular with respect to comparatively small particles.For example, frequencies in the region of 200 kHz, that is to say, fromapproximately 180 to 220 kHz, are used for cleaning with regard toparticles with a diameter of more than 1 μm. For the release ofparticles of even smaller diameters, the above-mentioned bandwidth canalso be extended further up to 2 MHz.

With regard to the acoustic power, 50 watts or more, up to, for example,2,400 watts is preferred. This is the case if it takes the form of acleaning application.

In the case of a level measurement, it is also possible to work withlower, even considerably lower, powers. For example, in the range of0.5-5 watts. However, in a level measurement a higher frequency ispreferably used. For example, in the range from 350 to 450 kHz,preferably from 370 to 390 kHz, and more preferably at 380 kHz.

However, level detection is also possible in the course of a cleaningapplication, and with the frequencies and powers described with respectto the latter, for which purpose vibrations generated by the pot areevaluated with regard to their decay characteristics, that is to say,for example, how quickly after termination of the application ofultrasound, the level of oscillation of the pot, which was previouslyexcited by the application of ultrasound, falls below a certainpredetermined level, so as to draw a conclusion on the mass that is inthe pot.

With regard to the cleaning behaviour and also, for example, the optionof fill level measurement most recently described, it is also sufficientif an ultrasound transmitter and an ultrasound receiver are just coupledto the metallic part of a pot.

They do not have to be in the interior of the wall. They can, therefore,in this respect be arranged in the pot exterior. However, if so desired,they can also be embedded in, and surrounded by, a plastic part, oranother protective part.

With regard to a level measurement with an ultrasound transmitterradiating into the interior of the pot, it is preferable if, when thepot is being conventionally used, the direction of the ultrasound beamis such that it has a downward angle with respect to the horizontal ofsome 30-70 degrees, preferably 40-60 degrees, and more preferablyapproximately 50 degrees.

FIG. 2 shows an electrical kitchen appliance 1 in accordance with asecond preferred example of embodiment of the invention. Instead ofusing an ultrasound signal, a determination of the fill level of thefoodstuffs 3 in the pot 2 here takes place by means of a strip-formheating element 15, which is preferably integrated into the wall 12 ofthe pot 2. This heating element 15 is activated and thus heated by aheating controller 13, which is provided in the base 7 of the electricalkitchen appliance 1. The heating element 15 is furthermore connected toa heating monitoring device 14, with which the heating behaviour of theheating element 15 can be detected. A heating signal that is a functionof the heating behaviour of the heating element 15 is then outputted bythe heating monitoring device 14 to a fill level checking device 16,with which the fill level of the foodstuffs 3 in the pot 2 can bechecked.

The principle of the level measurement consists in the fact that withconstant activation for purposes of heating the heating element 15, itsheating depends on how much heat can be delivered to the foodstuffs 3 inthe pot 2. The higher the fill level of the foodstuffs 3 in the pot 2,the greater is the volume of the foodstuffs 3 and thus the heat capacityof the foodstuffs 3, so that correspondingly more heat can be deliveredto the foodstuffs 3. This results in correspondingly lower heating ofthe heating element 15.

This heating behaviour, that is to say the degree of heating of theheating element 15, is determined by the heating monitoring device 14,which transmits a corresponding heating signal to the fill levelchecking device 16, which checks whether the fill level of thefoodstuffs 3 in the pot 2 lies above or below a maximum permissible fillheight, which allows a regular and safe operation of the electricalkitchen appliance 1.

In the present case, an electrical ohmmeter is provided as the heatingmonitoring device 14. With the electrical ohmmeter, the temperature ofthe heating element 15 is detected by way of the principle that theelectrical resistance of the heating element 15 increases as thetemperature of the heating element 15 increases. In accordance with anappropriate calibration, the temperature of the heating element 15 isdetected with the electrical ohmmeter, so that a permissible fill, ortoo high a fill, of the pot 2 with the foodstuffs 3 can be detected bymeans of the fill level checking device 16.

LIST OF REFERENCE SYMBOLS

-   1 Electrical kitchen appliance-   2 Pot-   3 Foodstuffs-   4 Lid-   5 Ultrasound transmitter-   6 Ultrasound receiver-   7 Base-   8 Central control unit-   9 Ultrasound controller-   10 Ultrasound evaluation device-   11 Surface-   12 Wall of the pot-   13 Heating controller-   14 Heating monitoring device-   15 Heating element-   16 Fill level checking device-   17 Pot edge-   18 Cable-   18′ Cable-   b Region-   I1 Line-   I2 Line-   H Internal height

The invention claimed is:
 1. A kitchen appliance (1) designed with anelectrical power supply, which has a pot (2) for purposes ofaccommodating foodstuffs (3) to be processed with the kitchen appliance(1), and forming a foodstuffs fill surface, wherein for purposes ofdetermining a fill level of the foodstuffs (3) in the pot (2) anultrasound transmitter (5) and an ultrasound receiver (6) are provided,and the pot (2) has a pot wall (12) with a wall thickness and acylindrical or conically developed internal surface, wherein theultrasound transmitter (5) and the ultrasound receiver (6) areintegrated into the pot wall (12) at an upper edge of the pot, so thatthe ultrasound transmitter (5) and the ultrasound receiver (6) arecaptive components of the pot (2), such that the ultrasound transmitter(5) and/or the ultrasound receiver (6) is arranged in a region of thecylindrical or conically developed internal surface for purposes oftransmitting or receiving ultrasound, the ultrasound transmitter (5)and/or the ultrasound receiver (6) forming a part of the cylindrical orconically developed internal surface, or the ultrasound transmitter (5)and/or the ultrasound receiver (6) is arranged within the wall thicknessof the pot wall (12) having the cylindrical or conically developedinternal surface, for purposes of applying ultrasound from above ontothe foodstuffs fill surface, and for purposes of receiving ultrasoundreflected upwards from the foodstuffs fill surface, wherein the pot (2)is mounted on a base (7) of the kitchen appliance (1), wherein anultrasound controller (9) together with an ultrasound evaluation unit(10) are provided in the base (7), wherein the ultrasound controller (9)is connected by a signal cable (I₁) to the ultrasound transmitter (5)and the ultrasound evaluation unit (10) is connected by a signal cable(I₂) to the ultrasound receiver (6), and wherein the cables (I₁, I₂)extend through the pot wall (12) from the ultrasound transmitter (5) andthe ultrasound receiver (6) at the upper edge (17) of the pot (2) to abottom of the pot (2) next to the base (7) of the kitchen appliance (1).2. The kitchen appliance in accordance with claim 1, wherein when thepot (2) is in a utilization position in the kitchen appliance (1) thepot is provided with an electrical power supply, with an electricalcable connection extending through the pot wall (12) between theultrasound transmitter (5) and/or the ultrasound receiver (6) so as toform an electrical connection.
 3. The electrical kitchen appliance inaccordance with claim 1, wherein the ultrasound transmitter (5) and theultrasound receiver (6) are part of a sensor ring formed at the upperedge of the pot (2), which has at least one further sensor.
 4. Theelectrical kitchen appliance in accordance with claim 1, wherein theultrasound controller (9) is configured for activating the ultrasoundtransmitter (5) such that the pot (2) is cleaned at the same time as thefill level is determined.
 5. The electrical kitchen appliance inaccordance with claim 1, wherein the ultrasound transmitter (5) and theultrasound receiver (6) are collectively designed as one transducer.